pip 命令：python包管理器-CFANZ编程社区

concat拼接

和+号一样

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var str = "xiaoming"
        // concat连接字符串
        var str1 = str.concat("qqqqqqqq")
        console.log(str1) 

    </script>
</body>
</html>

trim 去掉首尾空格

trimStart() trimLeft()去掉首空格

trimEnd() trimRight()去掉尾空格

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>

        var str = "   xiao ming    "


        // trim 去掉首尾空格
        // trimStart()    trimLeft()去掉首空格
        // trimEnd()    trimRight()去掉尾空格
        console.log("|"+str+"|")
        console.log("|"+str.trim()+"|")
        console.log("|"+str.trimStart()+"|")
        console.log("|"+str.trimEnd()+"|")
    </script>
</body>
</html>

split分割

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>

        // split 分割
        var str = "a,b,c,d"
        console.log(str.split(",")) 
    </script>
</body>
</html>

indexOf()和lastIndexOf()

能查到返回索引位置，不存在返回-1，返回找到的第一个值的索引

indexOf()从前往后查

lastIndexOf()从后往前查

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var str = "xiaoming"

        console.log(str.indexOf("i"))
        console.log(str.indexOf("w"))
        console.log(str.lastIndexOf("a"))
    </script>
</body>
</html>